Looking to build (or buy) an inductive proximity sensor that can detect copper bullets moving at around 900 m/s. My experience with circuits is small so forgive any misunderstandings in the following. I am always open to learning opportunities.
-Sensor composed of a wire coil, oscillator, Schmitt trigger (or just comparator?), and (maybe?) a demodulator. The signal from the sensor will be read by a microprocessor (right now I have an arduino uno)
-oscillator induces a current in the coil creating a magnetic field. When the copper passes through this field, the field changes, inducing a change in the current or affecting the oscillator in some way (need pointers on how this happens). Because the bullet is moving quickly, the sensor will have to react quickly. I believe this means the coil and oscillator needs low reactance and thus low inductance.
-the schmitt trigger (i think this is necessary over just a comparator because it can reduce the noise of the signal) will need to be able to detect small changes in the current and thus voltage. Not sure what magnitude but probably sub-microvolt differences. It also needs to have a fast slew rate (I think this is the term?) because the bullet travels through one centimeter in about 11 microseconds.
-not sure if the demodulator is necessary to convert information for the microprocessor to read or if the schmitt trigger can do this.
My two challenges at this point (other than overall understanding) are determining how the coil should be built and oriented and what device (both model and type) can be used to detect current changes.
TL;DR: want to detect quickly moving (900 m/s) copper with a magnetic field and some sort of amplifier (schmitt trigger?), need pointers on inductance in coils and detection devices
Thanks for any pointers!
-Sensor composed of a wire coil, oscillator, Schmitt trigger (or just comparator?), and (maybe?) a demodulator. The signal from the sensor will be read by a microprocessor (right now I have an arduino uno)
-oscillator induces a current in the coil creating a magnetic field. When the copper passes through this field, the field changes, inducing a change in the current or affecting the oscillator in some way (need pointers on how this happens). Because the bullet is moving quickly, the sensor will have to react quickly. I believe this means the coil and oscillator needs low reactance and thus low inductance.
-the schmitt trigger (i think this is necessary over just a comparator because it can reduce the noise of the signal) will need to be able to detect small changes in the current and thus voltage. Not sure what magnitude but probably sub-microvolt differences. It also needs to have a fast slew rate (I think this is the term?) because the bullet travels through one centimeter in about 11 microseconds.
-not sure if the demodulator is necessary to convert information for the microprocessor to read or if the schmitt trigger can do this.
My two challenges at this point (other than overall understanding) are determining how the coil should be built and oriented and what device (both model and type) can be used to detect current changes.
TL;DR: want to detect quickly moving (900 m/s) copper with a magnetic field and some sort of amplifier (schmitt trigger?), need pointers on inductance in coils and detection devices
Thanks for any pointers!